Portable electronic devices such as calculators and multipurpose computing platforms that can run software applications that provide calculator functionalities typically display information line by line (i.e., one line at a time). Such information may include numerical values that a calculator user enters using a user interface such as a keypad which includes number keys (i.e., buttons) as well as keys for mathematical binary operators and unary functions. Many calculators interpret keystrokes using an immediate execution mode. For binary operations (e.g., addition, subtraction, multiplication, division) in immediate execution mode, intermediate results are calculated as each key is pressed for each operation. The order of operations in mathematical expression is not taken into account by immediate execution mode calculators unless brackets or parentheses are supported by the calculator and utilized by the user. For unary operations (e.g., square root, reciprocal, exponents, etc.), the user keys the numerical value in first, followed by the unary operator. The immediate execution mode of operation compares with that utilized in formula-based calculators where the user types in an entire expression and then presses an “enter” key to evaluate the expression.
Most users find immediate execution mode calculators to be straightforward enough to use, particularly for short and simple calculations. However, even for simple calculations, mistakes can easily be made and be difficult to spot. Errors can occur using many current calculators for a variety of reasons and commonly result because of keystroke errors and/or use of an incorrect sequence of button pushes that misapplies precedence rules when performing calculations of expressions in which the order of operations affects the results. The inability to see prior entries before the current line and the fact that operators are not typically shown on the calculator's line-by-line display can compound difficulties because the user cannot see that an error was made or where in a given calculation it was made. Many calculators support use of a memory feature to help improve calculator functionality (and help address, for example some of the aforementioned issues in operation precedence) by enabling users to store a result of a calculation and then recall the result in a subsequent calculation. However, the number of available memories is typically limited in many consumer-oriented calculators to just one or two. In addition, the calculations used to create the stored results can still be prone to the errors that result from the limitations of the line-by-line display.
This Background is provided to introduce a brief context for the Summary and Detailed Description that follow. This Background is not intended to be an aid in determining the scope of the claimed subject matter nor be viewed as limiting the claimed subject matter to implementations that solve any or all of the disadvantages or problems presented above.